Sequence analysis of a cDNA coding for a pancreatic precursor to somatostatin.
A synthetic oligonucleotide having the sequence d(T-T-C-C-A-G-A-A-G-A-A) deduced from the amino acid sequence Phe-Phe-Trp-Lys of somatostatin-14 was used to prime the synthesis of a cDNA from channel catfish (Ictalurus punctatus) pancreatic poly(A)-RNA. The major product of this reaction was a cDNA fragment of 565 nucleotides. Chemical sequence analysis of the cDNA fragment revealed that it was complementary to a mRNA coding for somatostatin. The 565-nucleotide cDNA hybridizes strongly with a poly(A)-RNA estimated to be 1000 nucleotides in length. An amino acid sequence of the somatostatin precursor was predicted from the nucleotide sequence. Oyama et al. [Oyama, H., Bradshaw, R. A., Bates, O. J. & Permutt, A. (1980) J. Biol. Chem. 255, 2251-2254] have reported the isolation of a somatostatin from the catfish that is 22 residues in length (somatostatin-22). This peptide differs from somatostatin-14 in amino acid sequence. The cDNA sequence obtained by this laboratory codes for somatostatin-14 and predicts another somatostatin gene product from this species. Thus it would appear that there are at least two somatostatin gene products.